Ford Fiesta spring

Let me put it this way,
I you were say going for a long distance run on foot and wore one old trainer on one foot and one new trainer on the other just how would you feel the next day?
The better practice is to renew both springs at the same time.
Or both shoes for that matter.

Thanks.

I've put a new spring on the other side to match up. I noticed the spring was rusting in the same place. Where the other spring brock is this a common problem on the fiesta ?